I did note that you mentioned the cigars spent a couple weeks in the zip lock. Say the cigars had been over humidified their whole life, around 70-75% which is common for my B&Ms around here. I don't feel that 2 weeks in an an air tight bag at ~65% would be enough time collectively lower the sticks humidity.
Either way I'm sorry to hear you got a bad one, it bound to happen at some point. I wouldn't give up on LP as they have some great smoke. Its really hard to know what the true cause of this might have been.